[Cyberyeti]

 Tramticket, on 2019-August-13, 03:02, said:

I am not a great fan of simulations of play problems. So let's imagine that we go back to the traditional approach of planning the play and analysing the best line. Let's also assume that defenders have led a trump against our 7♥ contract (the traditional advice is to lead a passive trump against a grand slam and I think most human opponents would select a trump here).

You have 12 top tricks and your possible plays for the thirteenth are:
- A spade finesse (you draw trumps and can try for clubs 3-3 first)
- ruff out the clubs and establish a long club (♣Q, ♣A and ruff a club - succeeds if clubs are no worse than 4-2)
- A squeeze - you need the same player to hold the king of spades and the long clubs
[Others will tell me if I have missed another option!]

The chances of clubs being 3-3 or 4-2 are pretty good (about 84% I think), which is a bit better than the combined chance of 3-3 clubs and falling back on a finesse.

On this basis I would play to set up a long club (the line with the best chance) and go down!

This is why a double-dummy simulation is not a great tool - it will always select the winning line because it can see through the backs of the cards.

Learning to analyse the best line is a better tool and will help your card-play.

Then you're playing it very badly, draw trumps, discover the bad news in clubs, then use the diamond K as an entry to take the spade finesse which when you know W has 6 pointy suit cards to E's 10 is much better than a 50/50 proposition. There are also squeeze possibilities, but the club break and spade finesse are easily combinable.

Edit: I see Uwe got in before me, but remember dummy' small diamond is a key card. You are guaranteed to be able to make this contract if you read it correctly once east has 5 clubs, but it's not 100% to do this. The mechanism is that you come down to ♠AQ ♥x ♦x in hand ♠x ♦Kx ♣x in dummy and play the last trump, W has to keep his club, so if he has a small spade probably discards it, if he has the K discards a diamond, now you pitch dummy's club and if W has pitched a diamond, E must pitch a spade. Now you know he has 2 diamonds left so you play a diamond to dummy and a spade, and if he follows low, you drop his partner's K.

An expert W will see this coming and will not discard down to the obvious 1♠2♦1♣, unguarding diamonds early or discarding all his spades early to try to cause you to miscount.

[Tramticket]

 Cyberyeti, on 2019-August-13, 03:48, said:

Then you're playing it very badly, draw trumps, discover the bad news in clubs, then use the diamond K as an entry to take the spade finesse which when you know W has 6 pointy suit cards to E's 10 is much better than a 50/50 proposition. There are also squeeze possibilities, but the club break and spade finesse are easily combinable.

Edit: I see Uwe got in before me, but remember dummy' small diamond is a key card. You are guaranteed to be able to make this contract if you read it correctly once east has 5 clubs, but it's not 100% to do this. The mechanism is that you come down to ♠AQ ♥x ♦x in hand ♠x ♦Kx ♣x in dummy and play the last trump, W has to keep his club, so if he has a small spade probably discards it, if he has the K discards a diamond, now you pitch dummy's club and if W has pitched a diamond, E must pitch a spade. Now you know he has 2 diamonds left so you play a diamond to dummy and a spade, and if he follows low, you drop his partner's K.

An expert W will see this coming and will not discard down to the obvious 1♠2♦1♣, unguarding diamonds early or discarding all his spades early to try to cause you to miscount.

Thanks both. Yes I missed then extra possibilities when trumps are 2-2.

[Stephen Tu]

WTF does trumps 2-2 have anything to do with it? You have DK entry.

Trumps 3-1 or 4-0, draw all trumps, CQAK pitching a spade. If clubs broke 3-3 you are done, pitch another spade. If they broke 4-2 ruff a club and use DK to cash 13th club. If clubs 5-1 as actually happened then finesse.

[thepossum]

 Tramticket, on 2019-August-13, 03:02, said:

I am not a great fan of simulations of play problems. So let's imagine that we go back to the traditional approach of planning the play and analysing the best line.

That is my point Tranticket I like simulating play problems and comparing with experts. My sims are very basic constrained double dummy at the moment. As we all know double dummy bears no relation to real bridge play which is why the results of my simulation are higher than the real chances as assessed by advanced and expert players above. That is something that needs to be fixed in the obsession with double dummy AS people like Matthew Kidd have written even world class and expert players do not bid to or make all double dummy available slams and never will I imagine One thing I am curious about is whether expert assessments of percentages of slams are closer to world class/expert rates of making them than double dummy percentages

It was a good chance though and I missed it (maybe) by not being good enough (definitely) to think it through in an auction, and possibly not play it correctly. I thought I could be down two kings and wasnt confident.

For example anyone who tried two rounds of clubs before testing trumps was in trouble and I was lucky to have 2-2 trumps and a spade lead so I didnt have to think. For example what happens if I get a bad trump break after my second trump

PS Thanks to everyone for all your advice on how really to assess and play things

PPS I further investigated bad splits like above and with that shape of hands 7NT was close to 98% and 7H dropped to 84%, and now I'm trying to constrain it to a heart lead

PPPS Looking at how the few people actually made the grand. One player successfully squeezed East for Spades and Diamonds and made an extra diamond trick Well beyond me as are some of the above discussed options